String Fragmentation in Supercooled Confinement and Implications for Dark Matter

TL;DR

This paper explores how supercooled confinement transitions in the early universe can lead to enhanced production of composite dark matter particles through string fragmentation, significantly affecting their relic abundance.

Contribution

It introduces a novel model of string dynamics during supercooled confinement, revealing its impact on dark matter relic density and particle production in the early universe.

Findings

Enhanced composite state production due to string stretching

Significant increase in dark matter relic density

Implications for particle energetics and bubble-wall dynamics

Abstract

A strongly-coupled sector can feature a supercooled confinement transition in the early universe. We point out that, when fundamental quanta of the strong sector are swept into expanding bubbles of the confined phase, the distance between them is large compared to the confinement scale. We suggest a modelling of the subsequent dynamics and find that the flux linking the fundamental quanta deforms and stretches towards the wall, producing an enhanced number of composite states upon string fragmentation. The composite states are highly boosted in the plasma frame, which leads to additional particle production through the subsequent deep inelastic scattering. We study the consequences for the abundance and energetics of particles in the universe and for bubble-wall Lorentz factors. This opens several new avenues of investigation, which we begin to explore here, showing that the composite dark matter relic density is affected by many orders of magnitude.